Water Content-Controlled Formation and Transformation of Concomitant Pseudopolymorph Coordination Polymers

Abstract

Two concomitant pseudopolymorph coordination polymers {[Cd2L2(OAc)4]·2DMSO} n (1) and {[CdL(OAc)2]·2.75H2O} n (2) were synthesized by self-assembly of 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (L) and cadmium acetate in DMSO. Single-crystal X-ray diffraction confirmed that 1D ladder structural motifs exist for pseudopolymorphs 1 and 2 which contain DMSO and water guest molecules, respectively. Our study illustrated the active role of solvent water content in obtaining compound 2. We find that the presence of water as an impurity in the DMSO solvent creates the possibility of formation of concomitant pseudopolymorph coordination polymers which is a unique event. Furthermore, our analyses showed the effect of environmental humidity on the transformation of unstable compound 1. 1D ladder pseudopolymorphic compound 1 could be transformed to guest-free 1D linear compound [CdL(OAc)2(H2O)] n (3′) (the powder form of single crystals of 3) through a scarce case of water absorption from air. Also, the crystalline material of coordination polymer 3 was transformed to coordination polymer 2 through the dissolution–recrystallization structural transformation process in DMF or DMSO. Our study clarified that the amount of water in the reaction container can control the formation of one of the compounds 2 or 3. In the presence of a significant amount of water, compound 3 (coordinated water) will be produced, whereas if a small amount of water is present, compound 2 (uncoordinated water) is prepared as an exclusive product.

In Situ Conversion of Ligand to a Coordination Polymer via a Core@Shell Crystal: A Multi-Step Phase-Dependent Structural Transformation

“…Our structural analysis by the Rietveld method showed that two water molecules replaced coordinated methanol and acetonitrile molecules in 1 and 2 , respectively. A similar humidity-induced structural transformation has recently been reported by us. , …”

“…In special cases, this process can lead to chemical bond cleavage and the formation of new bonds for coordinated (solvent) molecules. Therefore, in some reports of single-crystal-to-single-crystal (SCSC) transformation, the change in the coordination environment of the metal can be observed. ,,− External stimuli, like humidity, , light, temperature, and mechanical forces can induce a structural transformation process. In particular, the water molecule as a green solvent can not only be added to the compound when crystals are immersed in water, but also participate in this process through the moisture absorbed from the air. ,,, It should be noted that SSST can affect the size of crystals, and in some cases, microcrystalline powder materials are produced (crystal-to-powder transformation). ,,, The significance of water as a source of life on earth and for health development is quite obvious.…”

“…In particular, the water molecule as a green solvent can not only be added to the compound when crystals are immersed in water, but also participate in this process through the moisture absorbed from the air. 38,71,76,77 It should be noted that SSST can affect the size of crystals, and in some cases, microcrystalline powder materials are produced (crystal-to-powder transformation). 38,71,76,78 The significance of water as a source of life on earth and for health development is quite obvious.…”

“…38,71,76,77 It should be noted that SSST can affect the size of crystals, and in some cases, microcrystalline powder materials are produced (crystal-to-powder transformation). 38,71,76,78 The significance of water as a source of life on earth and for health development is quite obvious. During the past decade, and due to the increase in the world's population, water scarcity has become a challenging global issue.…”

Synergistic Induction of Solvent and Ligand-Substitution in Single-Crystal to Single-Crystal Transformations toward a MOF with Photocatalytic Dye Degradation

“…Even though there are various examples of water-induced SCSC transformations reported up to date, this synergistic induction along with ligand-substitution is, however, relatively rare. Most of the water-triggered SCSC transformations involve dehydration/rehydration in which the water molecule played its role as ligand and/or guest molecules. − The completion of the 1a → 1b and 2a → 2b SCSC transformations was studied by PXRD (see Figure a,b). In addition, the BET (Brunauer–Emmett–Teller) surface areas of 1a , 1b , 2a , and 2b were determined to be 1.17, 4.70, 2.28, and 4.41 m 2 /g, respectively.…”